<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        * {
            margin: 0px;
            padding: 0px;
        }
        div{
            width: 300px;
        }
        div::after{
            content: "";
            display: table;
            clear: both;
        }
        ul{
            list-style: none;
        }
        li{
            width: 100px;
            height: 100px;
            float: left;
            background-color: pink;
        }
    </style>
</head>

<body>

    <div>
        <ul>
            <li>1</li>
            <li>2</li>
            <li>3</li>
            <li>4</li>
            <li>5</li>
        </ul>
    </div>

</body>

</html>